Dual-functionalized defective metal-organic frameworks for fast and sensitive biosensing of Salmonella

Accurate screening of pathogenic bacteria is effective to prevent foodborne diseases. In this study, a handheld biosensor was newly developed for sensitive detection of Salmonella inside a pipette tip using immune nickel meshes (INMs) for bacterial enrichment and fluorescent defective metal-organic frameworks with boronic acid (MOFs@B(OH)₂) for bacterial labeling. First, three INMs were respectively assembled in a 3D-printed conic separator inside a tip. Then, the mixture of bacterial sample and MOFs@B(OH)₂ was pipetted in and out, allowing the antibodies on INMs to capture flow-through target bacteria and MOFs@B(OH)₂ to label them for formation of INM-bacteria-MOFs@B(OH)₂ conjugates. Finally, acetic acid was pipetted to dissociate MOFs@B(OH)₂ from the conjugates, which was excited by 370 nm light and measured at 464 nm to determine target bacteria. Under optimal conditions, this biosensor enabled detection of Salmonella as low as 18.8 CFU/mL within 20 min, and showed potential for in-field pathogen screening.